trying to repair 4 wheel drive

I lost the 4 wheel drive in my '97 sierra with a 5.7 litre a while back. A local shop attempted to fix but could not trace the problem down far enough but they got the components to work (by jumpering power to them). When it first happened my indicating lights were acting funky. With the truck stuck in 2WD sometimes the indicating lights would flash (and solid at times) 4HI or 4LO. I was starting to blow the transfer case fuse until I eventually kept the fuse out. With the shop able to prove that the components worked and the funky light show I was sure that it was the tccm. I finally figured out how to get the tccm out and I tried mine in a friend's truck and it worked. That proves my tccm works. Last night I plugged my tccm back in and put the fuse bak in and nothing (like before). As I started the truck all 3 indicating lights turned on for about two seconds and than stayed off. I tried to press the 4HI and 4LO buttons to see if I could hear anything (like in my friend's truck) and nothing. Does anyone have any hints? I've printed everything I can from Alldata and I'm going to start tracing wires. I checked the grounds last night and they were good. One last thing is ever since I bought the truck in 2000 it has always been difficult to change from 2WD to 4WD. The 4WD button I would press would not start flashing (the 2WD light would still be solid). Eventually after numberous tries it would work. I noticed my friend's would catch right away.

Bob

encoder motor